Anyone coming back from seeing the pope in Mexico is urged to avoid donating blood. Federal health officials issued a warning saying it could spread the Zika virus.

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While the Zika virus is largely spread through mosquitoes, health officials believe it can also be transmitted through blood transfusions.

Along with Mexico, officials have also issued a warning for countries in Central and South America. They say if you've traveled to any of the affected areas, you should wait at least four weeks to donate blood.

They also say anyone who's had sex with someone who's been to these countries should wait four weeks as well.

"When the mosquito bites, there's an infectious period which right now is considered about seven days. They're adding the additional time so that any risk to blood is not there," said United Blood Services Regional Director Sergio Carrasco.

A handful of deaths have been linked to the Zika virus, but officials say that's very rare. It has also been linked to serious birth defects.